Re: [perfmon2] FLOPS on Nehalem

[Dr. V. K. <Vin...@sc...>]

Dear Stéphane,

stephane eranian a écrit :
> Vincent,
> 
> Hugh is right!
> Be careful than on Core i7, micro-ops are counted not instructions.

OK.

> Other users have also reported variations in the number of
> micro-ops reported for the same instruction. It depends on
> the floating point values passed and whether or not they
> reach the limit of their types (e.g., denormals).

OK, I modify the module accordingly to what Hugh said and it seems to be
quite OK (at least "enough" for a first prototype):

MXM:
Measured :	Perf : 4.818     [GFLOPS]
Computed : 	Perf : 4.383     [GFLOPS]

MXV:
Measured :	Perf : 1.329     [GFLOPS]
Computed : 	Perf : 1.172     [GFLOPS]

(the regular 10 % can be easily used as a correction)

> As for PFM_NHM_SEL_ANYTHR, it is not mandatory at all.
> In fact you probably don't want to use it. If you run pfmon
> on all logical cores (without --cpu-list), then you can compute
> total FLOPS by adding up each per-cpu counts. Alternatively
> you can use the --aggr option to have pfmon do it for you.

Heum, maybe my first post was not clear, sorry for that. I don't use the
"pfmon" tool. I implemented what I needed. My goal is to be able to
measure all the FLOP's (actual) on each (physical) core of a processor,
regardless of the application/thread/process which is running on. It is
why I thought I had to precise the PFM_NHM_SEL_ANYTHR flag in the
structure. Maybe I must have a look in the pfmon source code ?

Thanks again for your help

Cheers :)
Vince

-- 
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Dr. Vincent KELLER

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